How Much Water Should You Drink?

The facts about hydration, beauty and health.

Good old-fashioned H20 is one of your body’s most basic and vital needs. “It’s in our cells and in our blood and in all of the tissues in-between,” says Barbara Rolls, Ph.D., professor of Nutritional Sciences at Pennsylvania State University and a thirst expert.

Proper hydration helps our digestive system run smoothly, keeps our cells young and helps our immune system fight infection. So it would make sense that the more you guzzle, the healthier you’ll be, inside and out, right? Not exactly, says Rolls. “For most of us, fluid balance is not a problem." In other words, you’re getting enough water already, sans that fancy water bottle glued to your hand. It’s time to get real about water—read on to get the facts, not fiction.

Define…WaterExperts stress that we need to broaden what we think of as water. “Many people think that the only way to hydrate is with plain drinking water, but that’s just not true,” says Keith Ayoob, R.D., associate clinical professor of pediatrics at Albert Einstein College of Medicine in New York.

Currently, the National Institute of Medicine recommends that women get 2.7 liters (about nine cups) of water per day. But the suggested sources go beyond glasses of clear water. All beverages, including water, as well as moisture in foods like fruit, vegetables, lean meat and soups count.

8x8 RealityBut what about the 8 x 8 rule (drink eight glasses of eight ounces of plain water per day, on top of everything else)? There’s no scientific evidence backing that recommendation.

A Dartmouth physiologist named Heinz Valtin conducted a comprehensive search for the origin of this widely repeated statement and published his findings in the American Journal of Physiology in 2002.

Not only did he conclude that there was no evidence to suggest that healthy adults needed to drink large amounts of water, but he also found a possible reason for the long purported myth: a misinterpreted National Resource Council suggestion from 1945.

The original text stated: “A suitable allowance of water for adults is 2.5 liters daily in most circumstances. An ordinary standard for diverse persons is one milliliter for each calorie of food. Most of this quantity is contained in prepared foods.”

He suggested that the last sentence was possibly ignored and the statement as a whole interpreted as you must drink eight glasses (2.5 liters) of water each day.

Thirst ≠ DehydrationContrary to the popular myth, just because you’re thirsty doesn’t mean you’re already dehydrated. Dehydration occurs when the body loses more fluid than it takes in, but many people feel thirsty before they reach this deficit, says Rolls.

Two possible reasons for this disconnect: dry mouth and salty foods (more water is needed to dilute salt in the blood, so your thirst center sends an alert possibly causing you to feel thirsty). One small study followed young men around for a day, recording hydration markers in the blood and when they felt thirsty. Researchers found that the men felt thirsty before any actual fluid deficits occurred in their bodies.

Drinking Gallons of Water Won’t Hydrate Your Skin. At All.The amount of water you drink plays zero role in your skin’s appearance, says Amy Wechsler, MD, and YouBeauty Dermatology Advisor. Although it sounds like an easy fix, it won’t help combat dry skin or clear up your acne. Bummer!

The liquid water you consume passes through you (via urine) and has no effect on outward body surfaces. A report from the British Nutrition Foundation confirmed this myth as well, concluding that there was very little evidence connecting any amount of water consumption to skin appearance.

Eating Your Water May Be The Key to Long-Lasting Beauty…Some foods, like watermelons and cucumbers, are more than 90 percent water. Howard Murad, M.D. and author of "The Water Secret" believes that these water-heavy foods play a very important role in keeping you young and vibrant.

“Over the years, our cells naturally lose water and deteriorate, making it hard for our bodies to protect against the free radical damage that leads to aging,” says Murad. So, how does he suggest you replenish your water tank for optimal wellness? Don’t run to refill your water bottle.

“Water-packed foods, like colorful fruits and vegetables, are also filled with nutrients, which help your body hold onto the water long enough to put it to good use.”

…And Weight Loss!

Water-rich foods are also the star of Dr. Rolls’ book, "The Volumetrics Weight Control Plan," but under a weight loss lens. “Water is the magic ingredient,” she says. “When it’s bound into solid food, you can eat a much bigger portion for the same amount of calories.”

In one of Rolls’ studies, published in the American Journal of Clinical Nutrition, participants who ate a chicken rice soup were more satiated and consumed fewer calories at a later meal than those who ate a chicken rice casserole with a separate glass of water.

Both meals contained the exact same ingredients; the only difference being the water placement. Another bonus benefit to eating more hydrating foods: Water hangs out in really healthy foods that many of us aren’t getting enough of, like lean proteins, high fiber foods and fish, says Rolls.

When You DO Need More AguaAlthough you may be rethinking those constant trips to the water cooler with your BPA-free reusable bottle, rest assured, there are times you need to increase your intake.

If you live in a hot, dry climate, are visiting a higher altitude than you’re used to or exercising outside in hot temperatures, you’ll need to get more than the recommended amount of water in your system, says Kristin Kirkpatrick, MS, RD, wellness manager for the Cleveland Clinic's Lifestyle 180 Program and YouBeauty Nutrition Advisor.

Also, the pressurized air in an airplane cabin consists of only 5 to 10 percent humidity (which can cause dry mouth and a scratchy throat) so you should always accept a non-alcoholic offer from the drink cart to replenish your fluids, says Ayoob. Your best options are water, any clear soft drink (they typically don’t contain caffeine) or club soda with a little cranberry juice.

Kirkpatrick points out that you don’t know how often the cart will come around, and those dinky little cups don’t hold enough water to replenish your fluids, so her airplane strategy is this: “The minute you get past security, buy an enormous bottle of water. Bring it onboard with you and take a sip every 15 to 20 minutes.”

Bottom line: Water is an amazing substance and it’s seriously everywhere—in our bodies, beverages and foods. Just follow your thirst mechanism (don’t stress about forcing down pints of plain water each day!) and up your water-rich food intake for optimal beauty and health.

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